**8. UNSCEAR 2017 Report**

functions of the leaves. Thus, the quality of the soil and air will affect the health of the larval

The decrease in plant quality for larvae may originate from two different causes: a decrease in certain favorable chemicals (e.g., essential nutrients) in leaves and an increase in unfavorable chemicals (e.g., reactive oxygen species and defense chemicals) in leaves. In the former scenario, the lack of an essential vitamin in the leaves may be fatal for butterfly larvae because larvae are dependent on vitamins that are supplied through the ingestion of leaves. A similar

of environmental pollution and destruction in Europe and North America; however, the pre-

The latter possibility of the decrease in plant quality for butterfly larvae may occur if plants are stressed by even low levels of exposure to radioactive materials; this exposure can produce reactive oxygen species, defense chemicals, or another substance that is harmful to larvae. Reactive oxygen species are known to be produced by various abiotic stressors, and the production of defense chemicals are induced by insect bites in many plants [81–83]; however, whether radiation stress can trigger such responses in *O. corniculata* and in plants in general is unknown. The upregulation of unfavorable chemicals and the downregulation of favorable

Consequently, biochemical changes in producers (i.e., plants) affect primary consumers (i.e., herbivorous animals) and then secondary consumers (i.e., carnivorous animals). These foodmediated effects of pollutants can radiate through an ecological food web, and it is indirect field effects that are different from the bioaccumulation paradigm. It is reasonable to imagine that damage to keystone species that have connections with many other species may cause relatively large effects on the ecosystem; however, recent research posits that anthropogenic disturbances on a small number of any species may cause instability in an ecosystem [84, 85].

Among the three modes of action of the field effects discussed above, the second mode (i.e., particulate matter) is associated with immunological responses that may be prominently problematic for humans because humans have very effective (and, thus, very sensitive) immunological systems, some of which insects do not have. A small amount of radioactive or nonradioactive aerosol from a nuclear reactor can potentially cause large and fatal physiological effects in some human individuals via immunological sensitization. However, immunological responses vary among individuals, and it is known that immunological sensitivity to chemicals (i.e., allergens) greatly varies among human individuals. However, once sensitized, humans can detect a remarkably small number of molecules and manifest allergic symptoms. It is possible that radioactivity denatures proteins, which makes naturally occurring proteins immunogenic. The protein-denaturing effect of ionizing radiation as well as its association with immunogenicity may be one of the important topics that should be experimentally tested. As a whole, these effects can collectively be called *the* 

) deficiency has been recognized as one of the major consequences

butterflies that eat the affected leaves.

cise causes of this deficiency are difficult to identify [77–80].

chemicals for larvae may occur simultaneously.

**7. Possible field effects on humans**

*immunological effects*.

case of thiamine (vitamin B1

58 New Trends in Nuclear Science

Because the field effects of "nuclear" pollution may be a new concept, at least to some extent, misunderstanding or confusion about this issue may prevail. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2017 Report [93] provides an example. This report mentioned our studies in paragraph 125, in which H8 refers to Hiyama et al. [9], and M9 and M10 refer to Møller et al. [19] and Møller et al. [20], respectively.

*125. The Committee had made reference to studies in which effects in various terrestrial biota had been observed in areas with enhanced levels of radioactive material as a result of the FDNPS accident [H8, M9, M10]. It had noted that the substantial impacts reported for populations of wild organisms from these studies were inconsistent with the main findings of the Committee's theoretical assessment. The Committee had expressed reservations about these observations, noting that uncertainties with regard to dosimetry and possible confounding factors made it difficult to substantiate firm conclusions from the cited field studies.*

It is understandable that our study is "inconsistent with the main findings of the Committee's theoretical assessment" (i.e., the dosimetric simulations). I agree that "uncertainties with regard to dosimetry" should be overcome in the near future; however, without precise dosimetric data, the findings that conclude the biological effects were correlated with the ground radiation dose and/or the distance from the nuclear reactors and that state the biological effects in the field were reproduced dose-dependently in laboratory experiments are entirely valid. The main reason for this discrepancy is the exclusion of the field effects in the UNSCEAR assessment. In contrast, our experiments were constructed to reflect real-world phenomena, including the direct effects and indirect field effects. Furthermore, contrary to the UNSCEAR statement above, there were no major confounding factors in our study [9] because it consisted of controlled laboratory experiments.

leaves for butterfly larvae. Because the larvae are highly resistant against the internal exposure to pure radioactive cesium (unpublished data), the high mortality and abnormality rates from the contaminated leaves can be largely attributed to the indirect field effects. It should be noted that what was measured in our experiments was the radioactivity concentration of radiocesium; however, other radioactive and nonradioactive materials were released from the Fukushima nuclear reactors, and these materials may have also contaminated the leaves. In this sense, *the radioactivity concentrations of radiocesium can be considered as an indicator of the degree of the pollution*. This is an important difference from the conventional dosimetric approach. To our knowledge, quantitative toxicological data that reflected some of the field effects were available only for butterflies. Thus, it is interesting to apply these data to humans to roughly grasp the collective effects of the Fukushima nuclear accident. Although there is no rigorous reason to believe that the butterfly data are applicable to humans, this attempt can be justified because of the lack of human-specific data and data from other organisms that reflect

Understanding Low-Dose Exposure and Field Effects to Resolve the Field-Laboratory Paradox…

The basic experimental strategy was to collect the polluted food (i.e., plants) from Fukushima and feed the plant samples to butterfly larvae from Okinawa, which was the least polluted locality in Japan. When non-contaminated leaves were fed to larvae, normal individuals emerged. However, when polluted leaves were fed to larvae, morphologically abnormal adults emerged, and the mortality of larvae and pupae was high. The abnormality rate and the mortality rate were then obtained for each polluted diet. Because the radioactivity concen-

*The half abnormality dose* (equivalent to median toxic dose, TD50; called TD50 hereafter) of radiocesium for the butterfly was first obtained in Nohara et al. [10] based on the power function fit for data points from relatively high-dose diets. Later, the data points from the relatively low-dose diets were added to the previous data [11]. The mathematical model fits for these combined data were performed using the power function and Weibull function models [12]; the sigmoidal data fit with the Weibull function model yielded a TD50 value of 0.45 Bq body−<sup>1</sup> (meaning that a cumulative dose of 0.45 Bq per larva results in abnormality or death in 50% of

The mean body weight of larvae was 0.0346 g. Therefore, the TD50 can be read as 13 kBq kg−<sup>1</sup> body weight. Here, I assume an average Japanese male person (30–49 years old) has a body weight of 68.5 kg, according to a survey by the Ministry of Health, Labour and Welfare [94].

when nutritional balance is maintained [95].

Based on these data, the radioactivity concentration of diets required to reach the TD50 value in a given time span in a Japanese male human can be calculated (**Figure 3a**). To consume 890.5 kBq in 1 day, 890.5 kBq must be contained in a 1.555 kg diet; thus, the radioactivity

body weight is multiplied by 68.5 kg body weight, result-

for an average Japanese male human. This average person

diet must be consumed to reach the TD50 value in 1 day. To

diet are required to reach the TD50 value in 10 years and

diet is mostly negligible for this average person

diet) and the amount of food

http://dx.doi.org/10.5772/intechopen.79870

61

.

diet is required. Similarly, a

both the direct effects and indirect field effects.

For this average person, 13 kBq kg−<sup>1</sup>

ing in a TD50 of 890.5 kBq body−<sup>1</sup>

concentration of 573 kBq kg−<sup>1</sup>

eats 1.555 kg diet day−<sup>1</sup>

157 Bq kg−<sup>1</sup>

tration of radiocesium species (134Cs plus 137Cs) in foods (Bq kg−<sup>1</sup>

consume 890.5 kBq within 1 year (365 days), a 1.57 kBq kg−<sup>1</sup>

diet and a 15.7 Bq kg−<sup>1</sup>

100 years, respectively. Clearly, a 15.7 Bq kg−<sup>1</sup>

that each larva ate (g) was available, a dose-response curve was obtained [12].

the population). A loose threshold was detected at approximately 10 mBq body−<sup>1</sup>

Moreover, the UNSCEAR statement completely ignores the process of logical judgment in terms of the cause of the Fukushima nuclear accident. The causality of the effects of the accident should be evaluated systematically according to logical postulates such as "the Postulates of Pollutant-Induced Biological Impacts" [45]. This includes six clauses that must be met to prove the causality of the pollutant(s) from a given source, i.e., spatial relationship, temporal relationship, direct exposure, phenotypic variability or spectrum, experimental reproduction of external exposure, and experimental reproduction of internal exposure [45]. The causality should not be judged solely from a dosimetric standpoint.

The UNSCEAR 2017 Report [91] further commented on our paper in paragraph 134, in which H9 and O12 refer to Hiyama et al. [14] and Otaki [48], respectively.

*134. Hiyama et al. [H9] provided further evidence to suggest that the high abnormality rates observed in the pale grass blue butterfly were induced by "anthropogenic radioactive mutagens." However, Otaki [O12] synthesized the results from several studies of the effects on the same species of butterfly following the FDNPS accident, and reported that ionizing radiation was unlikely to be the exclusive source of the environmental disturbances observed.*

The above comments on our research are misleading; specifically, the last sentence wrongly implies that "the environmental disturbances observed" were caused by unknown confounding factors that were not related to the Fukushima nuclear accident. Rather, in Otaki [48], I mentioned the importance of the field effects from both radioactive and nonradioactive materials from the Fukushima Dai-ichi Nuclear Power Plant. In other words, "ionizing radiation" (i.e., the direct effects in the context of Otaki [48]) was not the exclusive source. It is entirely valid to say that the high abnormality and mortality rates observed in the butterfly were caused by the pollutants from the Fukushima nuclear accident. This UNSCEAR case indicates the low level of understanding regarding the field effects and the lack of fundamental logic among the researchers who contributed to the formulation of these paragraphs in the UNSCEAR 2017 Report [93]. On the other hand, these misleading comments may be understandable, considering that we presented the topic of indirect field effects only briefly in our previous papers. There is an urgent need for more precise explanations and experimental validation of this issue.
